Titanium Dioxide Nanomaterials: Synthesis, Properties, Modifications, and Applications

2.3. Evaluation of Photocatalytic Water Splitting 6507 2.3.1. Photocatalytic Activity 6507 2.3.2. Photocatalytic Stability 6507 3. UV-Active Photocatalysts for Water Splitting 6507 3.1. d0 Metal Oxide Photocatalyts 6507 3.1.1. Ti-, Zr-Based Oxides 6507 3.1.2. Nb-, Ta-Based Oxides 6514 3.1.3. W-, Mo-Based Oxides 6517 3.1.4. Other d0 Metal Oxides 6518 3.2. d10 Metal Oxide Photocatalyts 6518 3.3. f0 Metal Oxide Photocatalysts 6518 3.4. Nonoxide Photocatalysts 6518 4. Approaches to Modifying the Electronic Band Structure for Visible-Light Harvesting 6519

Semiconductor-based Photocatalytic Hydrogen Generation

TiO2 photocatalysis and related surface phenomena

https://dc.engconfintl.org/cgi/viewcontent.cgi?article=1032&context=superalloys_ii

A critical review of high entropy alloys and related concepts

On the significance of the H/E ratio in wear control: a nanocomposite coating approach to optimised tribological behaviour

Multi-element high-entropy alloys are alloy systems with n (5≤n≤13) principal elements each having an atomic percentage no more than 35%. Using the alloys of Fe-Co-Ni-Cr-Cu-Al-Mn and Fe-Co-Ni-Cr-Cu-Al0.5 as target material in reactive sputtering, nitride films were deposited. The hysteresis curves of the two high-entropy alloys in reactive sputtering are quite different in comparison to those of elements or simple alloys. The film deposition rate decreased with increasing nitrogen gas flow and the highest film thickness was in excess of 2.5 μm. The alloy films are crystalline with structures of a mixed FCC and BCC or simple FCC solid solution, while the crystallinity of the nitride films decreased and approached amorphous with increasing nitrogen gas flow. The composition of the alloy films was similar to their original targets, and the nitrogen content of the nitride films increased with increasing nitrogen flow, to a maximum of 41.1 at.% nitrogen. The values of resistivity of the two alloy films were 108 and 135 μΩ cm, respectively, and those of their nitride films increased with nitrogen flow, to a factor of 3 of the alloy film. The rms surface roughness measured by AFM decreased significantly from 9 to 13 nm for the alloy films to only 1–3 nm for the nitride films. Values of hardness are about 4 GPa for alloy films and about 11 GPa for nitride films. The growth rate, the resistivity, and the hardness of the resulting nitride films were not affected too much by substrate bias due to the amorphous nature of the nitride films.

Nanostructured nitride films of multi-element high-entropy alloys by reactive DC sputtering

An in situ electron paramagnetic resonance (EPR) study has been carried out for anatase (Hombikat UV100) and rutile TiO2 nanoparticles at liquid helium (He) temperature (4.2 K) under UV irradiation. Rutile titania was synthesized by ultrasonic irradiation with titanium tetrachloride (TiCl4) as the precursor. XRD and Raman results evidence the crystallinity of titania phases. The nature of trapped electrons and holes has been investigated by EPR spectroscopy under air and vacuum conditions. Illumination of TiO2 powder (anatase and rutile) at 4.2 K resulted in the detection of electrons being trapped at Ti4+ sites within the bulk and holes trapped at lattice oxide ions at the surface. The stability of electron traps was very sensitive to temperature in both phases of TiO2. The annealing kinetics of the EPR detected radicals has been studied from 4.2 K to ambient temperature and also for calcined titania particles from 523 to 1273 K.

EPR investigation of TiO2 nanoparticles with temperature-dependent properties.

Deposition of carbon nitride thin films on Si(100) and polycrystalline Zr substrates was performed by dc magnetron sputtering of a graphite target under a pure nitrogen ambient. The resulting carbon nitride films (CNx) are primarily amorphous with a small volume fraction of nanocrystallites. Both energy‐dispersive x‐ray analysis and electron energy loss spectroscopy measurements showed that the amorphous matrix has uniform nitrogen‐to‐carbon ratios ∼0.4–0.8 depending on deposition conditions. Carbon and nitrogen K edge structures obtained from electron energy loss spectroscopy studies suggest that the amorphous carbon nitride matrix is primarily sp2 bonded. Apart from the carbon–nitrogen stretching vibration, Raman spectra of CNx films closely resemble those of diamondlike carbon films. Intensity and peak width changes of Raman features in the 1300–1600 cm−1 range due to inorganic carbon (D and G peak) under different deposition conditions are explained in terms of the extent of structural disorder in the...

Analytical electron microscopy and Raman spectroscopy studies of carbon nitride thin films

The antibacterial activity of photocatalytic titanium dioxide (TiO2) substrates is induced primarily by UV light irradiation. Recently, nitrogen- and carbon-doped TiO2 substrates were shown to exhibit photocatalytic activities under visible-light illumination. Their antibacterial activity, however, remains to be quantified. In this study, we demonstrated that nitrogen-doped TiO2 substrates have superior visible-light-induced bactericidal activity against Escherichia coli compared to pure TiO2 and carbon-doped TiO2 substrates. We also found that protein- and light-absorbing contaminants partially reduce the bactericidal activity of nitrogen-doped TiO2 substrates due to their light-shielding effects. In the pathogen-killing experiment, a significantly higher proportion of all tested pathogens, including Shigella flexneri, Listeria monocytogenes, Vibrio parahaemolyticus, Staphylococcus aureus, Streptococcus pyogenes, and Acinetobacter baumannii, were killed by visible-light-illuminated nitrogen-doped TiO2 substrates than by pure TiO2 substrates. These findings suggest that nitrogen-doped TiO2 has potential application in the development of alternative disinfectants for environmental and medical usages.

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Visible-light-induced bactericidal activity of a nitrogen-doped titanium photocatalyst against human pathogens.

Carbon nitride (CNx) thin films were prepared by dc magnetron sputtering of a graphite target in a nitrogen ambient onto Si(100) substrates held at ambient temperatures. The films are amorphous with a small volume fraction of nanocrystallites. All CNx coatings grown to a thickness of 1.5 μm are adherent and smooth. Nanoindentation studies showed clear dependence of hardness and effective modulus on deposition process parameters (nitrogen pressure, target power, and substrate bias). Most striking is the observation that CNx films can be synthesized with yield strength exceeding 5 GPa.

Ming-Show Wong

Papers

Nanostructured nitride films of multi-element high-entropy alloys by reactive DC sputtering

EPR investigation of TiO2 nanoparticles with temperature-dependent properties.

Analytical electron microscopy and Raman spectroscopy studies of carbon nitride thin films

Visible-light-induced bactericidal activity of a nitrogen-doped titanium photocatalyst against human pathogens.

Nano‐indentation studies of ultrahigh strength carbon nitride thin films